For years emulsified bitumens have been mixed with aggregates to form paving compositions. These emulsions are designated primarily as medium and slow setting types and are classified as anionic, cationic, or non-anionic. They comprise normally from about 60% to about 75% of a bitumen suspended in water with the aid of emulsifying agents.
If the aggregate that is to be mixed with the emulsion contains a large amount of surface moisture, the emulsion, which normally contains about 25% to about 40% of water, is diluted to such an extent that if it may be difficult to deposit sufficient bitumen from the emulsion onto the surface of the aggregate particles, or under certain conditions, the emulsion may completely wash away.
In preparing an anionic emulsion, a chemical emulsifier is used which is normally formulated by reacting a fatty acid or a rosin acid with an alkali to produce the water soluble emulsifier. In preparing cationic emulsions, the emulsifier is prepared by reacting amines or an imidazoline with an acid such as hydrochloric acid to produce the emulsifier. Non-anionic emulsions are prepared using an emulsifier such as an organic polyglycol ether.
It is an object of this invention to prepare a bituminous emulsion which is medium setting and is not nonionic but possesses both anionic and cationic characteristics as described by the ASTM D-244 particle charge test used to identify the ionic character of an asphaltic emulsion. It is the further object of the invention to provide such an emulsion which will have improved mixing capabilities with a wide variety of aggregates, which can be mixed with such aggregates when they are either in a wet or dry condition, and which will have improved adhesive characteristics.